The volume of products being sorted and transported by material handling systems is rapidly increasing in the United States and worldwide. Much of the volume increase can be attributed to the growth of e-commerce, whereby products are purchased over the Internet by consumers and businesses and delivered from fulfillment centers where individual orders are picked from shelved stock, packed and shipped directly to the purchaser, without the intermediation of physical retail stores. The majority of e-commerce shipments are below the scale of cases or pallets in size and weight.
Automatic sortation systems are a key technology enabling fulfillment centers and shipping organizations to prepare high volumes of orders for shipment and move them through a sometimes-complex physical distribution system to the purchaser. High speed, low cost, and automated operations are key attributes for efficiency and competitiveness. Two of the most common sorter types are the loop sorter and the linear sorter.
A loop sorter is typically housed in a large building and resembles a small train with multiple package-holding segments (hereinafter “cars” or “sorter trays”) moving around a closed loop at speed. At one part of the loop, packages are moved onto individual cars at what are called “induction stations.” The packages at any given induction station may have a variety of shapes and/or sizes. As the sorter cars move around the loop, there are a multitude of locations called “sort points” where the contents of the train can be moved off, or “sorted,” into containers or attached conveyors. Various methods are used to move the product off the sorter car. Methods include tipping the car to the side, driving a transverse conveyor belt on top of the car, and dropping the product through the car via “bomb bay” doors.
Linear sorters perform the same transport and sorting function as loop style sorters. Linear sorters induct articles onto a single straight-line conveyor where all packages enter at the head of the sorter and are then expelled to containers positioned on the right or left of the sorter spine. The conveyor has features that move packages to the right or left at a precise time to discharge them into a waiting container or further conveyor designated by the sorter system. Typical discharge methods include “shoes” whereby features embedded in the conveyor move right or left to push the package off the conveyor, and “pushers” whereby a stationary actuator external to the conveyor pushes the package at the right moment off of the conveyor to the right or left.
In more recent years, a different type of sorter has been developed that utilizes a conveyor belt composed of many plastic or metal links with multiple rotating or otherwise moveable elements embedded in the conveyor belt structure. The tops of the moveable elements contact the product being transported and the bottoms of the elements contact fixed or moving features underneath the conveyor belt. When these elements touch features underneath the conveyor belt, their movement can be controlled, thus changing the movement of the article on the top surface to divert it off the conveyor. The conveyor belt can be long, e.g. a single belt for the entire sorter, or the belt can be broken into shorter sections whose actions must be coordinated to obtain the desired number of discharge points for the sorter.
New designs, e.g. U.S. patent application Ser. No. 15/916,248, filed Mar. 3, 2018, indicate how short sections of such linked belts can be used to build individual sortation modules, and multiple independent modules, each capable of moving a package off the conveyor, can be connected together to form sorters of different lengths. A sorter composed of modular units may be configured to accommodate varying initial sort point and package size requirements, and modules can be readily added or removed to accommodate changing needs.